1,496 research outputs found
Incoherent boundary conditions and metastates
In this contribution we discuss the role which incoherent boundary conditions
can play in the study of phase transitions. This is a question of particular
relevance for the analysis of disordered systems, and in particular of spin
glasses. For the moment our mathematical results only apply to ferromagnetic
models which have an exact symmetry between low-temperature phases. We give a
survey of these results and discuss possibilities to extend them to some
situations where many pure states can coexist. An idea of the proofs as well as
the reformulation of our results in the language of Newman-Stein metastates are
also presented.Comment: Published at http://dx.doi.org/10.1214/074921706000000176 in the IMS
Lecture Notes--Monograph Series
(http://www.imstat.org/publications/lecnotes.htm) by the Institute of
Mathematical Statistics (http://www.imstat.org
PMI: A Delta Psi(m) Independent Pharmacological Regulator of Mitophagy
Mitophagy is central to mitochondrial and cellular homeostasis and operates via the PINK1/Parkin pathway targeting mitochondria devoid of membrane potential (ΔΨm) to autophagosomes. Although mitophagy is recognized as a fundamental cellular process, selective pharmacologic modulators of mitophagy are almost nonexistent. We developed a compound that increases the expression and signaling of the autophagic adaptor molecule P62/SQSTM1 and forces mitochondria into autophagy. The compound, P62-mediated mitophagy inducer (PMI), activates mitophagy without recruiting Parkin or collapsing ΔΨm and retains activity in cells devoid of a fully functional PINK1/Parkin pathway. PMI drives mitochondria to a process of quality control without compromising the bio-energetic competence of the whole network while exposing just those organelles to be recycled. Thus, PMI circumvents the toxicity and some of the nonspecific effects associated with the abrupt dissipation of ΔΨm by ionophores routinely used to induce mitophagy and represents a prototype pharmacological tool to investigate the molecular mechanisms of mitophagy
Swelling and Softening of the Cowpea Chlorotic Mottle Virus in Response to pH Shifts
AbstractCowpea chlorotic mottle virus (CCMV) forms highly elastic icosahedral protein capsids that undergo a characteristic swelling transition when the pH is raised from 5 to 7. Here, we performed nano-indentation experiments using an atomic force microscope to track capsid swelling and measure the shells’ Young’s modulus at the same time. When we chelated Ca2+ ions and raised the pH, we observed a gradual swelling of the RNA-filled capsids accompanied by a softening of the shell. Control experiments with empty wild-type virus and a salt-stable mutant revealed that the softening was not strictly coupled to the swelling of the protein shells. Our data suggest that a pH increase and Ca2+ chelation lead primarily to a loosening of contacts within the protein shell, resulting in a softening of the capsid. This appears to render the shell metastable and make swelling possible when repulsive forces among the capsid proteins become large enough, which is known to be followed by capsid disassembly at even higher pH. Thus, softening and swelling are likely to play a role during inoculation
Information systems for development planning
In this paper the changing approaches to development planning are
described, from the economic-growth oriented strategies of the 1950s and the
1960s to the contemporary emphasis on alleviating poverty and meeting basic
needs. The process of development planning includes several phases; the
identification of aims, analysis, plan formulation and detailed design,
Implementation, controls, updating, and feedback and adjustment. This process
has become much more sophisticated in recent years, but in general, the
comprehensiveness and refinement of a development plan depends on the type
and scope of the data available. At the same time, the very process of
planning may reveal deficiencies In data and thus act as an incentive to
improved information gathering.
Three information systems are needed for development planning:
a resources information system, whose importance has been recognised for some
time but which has frequently consisted of a series of isolated and uncoordinated
inventories and studies; a scientific and technological information system'
and a management information system, whose Importance has frequently been
neglected.
Information in these areas must be collected, communicated to
government policy makers and administrators to meet their immediate needs, and
stored in a convenient and coordinated form so that it will be accessible in
the future. More global surveys and inventories will be needed during the
eiarly stages of development planning, and detailed project and programme
surveys will be needed during the design and implementation stages
Signature of Obliquity and Eccentricity in Soil Chronosequences
Periodic shifts in Earth\u27s orbit alter incoming solar radiation and drive Quaternary climate cycles. However, unambiguous detection of these orbitally driven climatic changes in records of terrestrial sedimentation and pedogenesis remains poorly defined, limiting our understanding of climate change‐landscape feedbacks, impairing our interpretation of terrestrial paleoclimate proxies, and limiting linkages among pedogenesis, sedimentation, and paleoclimatic change. Using a meta‐analysis, we show that Quaternary soil ages preserved in the modern record have periodicities of 41 and 98 kyr, consistent with orbital cycles. Further, soil ages predominantly date to periods of low rates of climatic change following rapid climate shifts associated with glacial‐to‐interglacial transitions. Soil age appears linked to orbital cycles via climate‐modulated sediment deposition, which may largely constrain soil formation to distinct climate periods. These data demonstrate a record of widespread orbital cyclicity in sediment deposition and subsequent pedogenesis, providing a key insight into soil‐landscape evolution and terrestrial paleo‐environment changes
Infinitely many states and stochastic symmetry in a Gaussian Potts-Hopfield model
We study a Gaussian Potts-Hopfield model. Whereas for Ising spins and two
disorder variables per site the chaotic pair scenario is realized, we find that
for q-state Potts spins [{q(q-1} \over 2]-tuples occur. Beyond the breaking of
a continous stochastic symmetry, we study the fluctuations and obtain the
Newman-Stein metastate description for our model.Comment: latex, 17 page
High-Latitude HI in the Low Surface Brightness Galaxy UGC7321
From the analysis of sensitive HI 21-cm line observations, we find evidence
for vertically extended HI emission (|z|<~2.4 kpc) in the edge-on, low surface
brightness spiral galaxy UGC7321. Three-dimensional modelling suggests that the
HI disk of UGC7321 is both warped and flared, but that neither effect can fully
reproduce the spatial distribution and kinematics of the highest z-height gas.
We are able to model the high-latitude emission as an additional HI component
in the form of a ``thick disk'' or ``halo'' with a FWHM~3.3 kpc. We find
tentative evidence that the vertically extended gas declines in rotational
velocity as a function of z, although we are unable to completely rule out
models with constant V(z). In spite of the low star formation rate of UGC7321,
energy from supernovae may be sufficient to sustain this high-latitude gas.
However, alternative origins for this material, such as slow, sustained infall,
cannot yet be excluded.Comment: to appear in the August 20 Astrophysical Journal; 17 pages; version
with full resolution figures available at
http://cfa-www.harvard.edu/~lmatthew
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